At first he was a bit square-looking for his new San Francisco bandmates, but his peculiar sense of humor won them over. (When told to shave his mustache, he shaved one side so that the band members could look at him from that angle.) He tended (sometimes to drummers' dismay) to treat the bass as more like a guitar than a part of the rhythm section, and was praised for this style by critics.

As the Jefferson Airplane became famous, Jack and Jorma formed a side project in 1969, Hot Tuna, and the two tended to be a pair supporting one another in disagreements with their bandmates. When Jorma left Jefferson Airplane in 1972, Jack went too. Hot Tuna lasted for several more years before breaking up in the late 1970s.

Jack then formed his own band, SVT, which was not too successful. In the mid-to-late 1980s he went back with his old bandmates in the KBC band (KantnerBalin Casady), and then in a one-time Jefferson Airplane reunion album and tour. In the 1990s he's played with Jorma in a new version of Hot Tuna and also in a semi-reunited band called Jefferson Starship -- The Next Generation. Jack has been an instructor at Jorma's guitar camp, the "Fur Peace Ranch", and has also released a bass guitar instruction videotape simply called "Bass Guitar of Jack Casady."
Sources: http://www.starship.pp.se/bio/jack_casady.html and http://www.theadvocate.com/enter/story.asp?StoryID=3600